Generally, graphene is a material with a honeycomb structure of an atomic size made of carbon atoms and may be made of raw materials containing carbon atoms such as graphite, carbon dioxide, ethanol, and methane and is a material having the most excellent characteristic among exiting materials.
The graphene has a small thickness of 0.2 nm, has high transparency, and may transfer 100 times more current than copper at room temperature 100 times faster than silicon. The graphene is more than twice higher than diamond with the highest thermal conductivity.
The graphene is more than 200 times stronger in mechanical strength than steel, but does not lose its electrical conductivity due to good elasticity even when being stretched or folded. Because of these excellent characteristics, the graphene is a next-generation material that can be applied to wearable computers as well as flexible displays and transparent computers, which are in the limelight as a future technology.
The most notable feature is that when electrons move on the graphene, electrons flows as if the mass is zero, which means that the electrons flow at a moving speed of light in the vacuum, that is, a luminous flux. The grapheme has an abnormal half-integer quantum hall effect on electrons and holes.
Such graphene may be fabricated mainly using a chemical vapor deposition process. That is, high-quality graphene may be mass-produced by the chemical vapor deposition method. The graphene may be deposited on a silicon wafer substrate or a metal substrate on which a metal catalyst layer is formed. As such, the graphene deposited on the substrate may be transferred and used onto a substrate made of a desired material.
A general method for transferring graphene has used a method of transferring graphene on a metal substrate onto a desired substrate by using a thermal release film in the air. At this time, a metal substrate, that is, a metal layer on the back surface of the graphene transferred onto the thermal release film is removed by a wet etching process. Thereafter, the graphene transferred onto the thermal release film may be transferred onto a target substrate by applying heat to the thermal release film.
However, when a series of transfer processes using the thermal release film is performed in the atmosphere, bubbles are generated between the thermal release film and the graphene, and between the graphene and the target object. At this time, the bubbles between the thermal release film and the graphene cause a phenomenon that the graphene is separated together when the metal substrate is etched, and the bubbles between the graphene and the target object impede the adhesion between the graphene and the target substrate to suppress the graphene from being completely transferred to the target substrate.
When bubbles or foreign substances are interposed between the graphene and the thermal release film or between the graphene and the target substrate in this way, the adhesion due to the transfer decreases and the quality of the graphene deteriorates.